The synaptic transmission mechanism at the cellular level and its contribution to information processing in a synaptic organization at a system's level are studied in a preparation where all the neurons involved are identifiable and accessible. Synaptic transmission is investigated in a flight system of Drosophila composed of a limited number of neurons and muscle fibers. All of the neurons and muscle fibers are morphologically and physiologically identifiable. With this advantage, the transmission mechanisms is studied at both the peripheral and central synapses of all of the component units. The information-processing mechanism of this system which furnishes coordinated motor output is then studied. Besides studying normal preparations, genetic techniques (single-gene mutation, mosaic formation, etc.) are used to create synapses and neuronal organization suitable for specific research such as the temperature controllable synapse for the study of the transmitter release mechanism. With physiological techniques (quantum content, equilibrium potential, conductance measurement, iontophoretic application of transmitter-related substances, etc.), transmitter release, ionic permeability changes at the postsynaptic membrane, and action of transmitter-related substances are studied at each synapse. The interrelations among neurons in the system are then studied to disclose the system's function to furnish the coordinated motor output pattern. With morphological techniques (light and electron microscopy, intra- and extracellular application of horseradish peroxidase, marker dyes, and silver impregnation), the exo- and endoytosis mechanism related to the presynaptic release mechanism and synaptic organization of the system are investigated. The result will elucidate the basic mechanism of transmission and that of the information processing, thereby interpreting the principle of peripheral and central nervous function.